Field of the Invention
The present invention relates to an imaging technique, and in particular to an ophthalmic imaging apparatus having an interference optics system used in, for example, an ophthalmic practice, a control method therefor, and a non-transitory computer-readable storage medium.
Description of the Related Art
Today, ophthalmic equipment provided with an optical device comes in a variety of forms. For example, various devices, such as an anterior ocular segment imaging device, a fundus camera, and a scanning laser ophthalmoscope (SLO), are used as optical devices for eye observation. In particular, an optical coherence tomography (OCT) apparatus (hereinafter referred to as an OCT apparatus) obtains high-resolution tomographic images of a specimen, and is emerging as essential ophthalmic equipment in the specialty of retinal medicine for outpatients.
The OCT apparatus performs high-sensitivity measurement by irradiating a sample (an object) with low-coherence light and utilizing reflected light from the sample and an interferometer. Furthermore, the OCT apparatus can obtain high-resolution tomographic images by scanning the entire sample irradiated with the low-coherence light. In this way, high-resolution tomographic images of the retina in the fundus of an examined eye can be produced through imaging. For the foregoing reasons, the OCT apparatus is widely used in, for example, ophthalmic diagnosis involving the retina.
Additionally, with the use of an apparatus incorporating the configurations of the OCT apparatus and the SLO, an examiner can perform imaging to produce a tomographic image of a desired segment while viewing a frontal fundus image of the examined eye (a fundus image). Meanwhile, a scheme is disclosed for generating a frontal fundus image based on the spectral intensity of an interference signal obtained by an OCT apparatus without incorporating the SLO configuration (Japanese Patent Laid-Open No. 2011-215134). Also, there is an apparatus that switches between OCT imaging modes in accordance with the depth of a segment to be imaged. This apparatus switches between a vitreous body mode and a choroid mode based on the distance from the position in which the optical path length of measurement light and the optical path length of reference light match to a predetermined boundary in a tomographic image of the fundus. In this way, a tomographic image of a vitreous body side and a tomographic image of a choroid side can be observed appropriately in the vitreous body mode and the choroid mode, respectively (Japanese Patent Laid-Open No. 2012-223264).
In recent years, as in Japanese Patent Laid-Open No. 2011-215134, there is an OCT apparatus which does not incorporate the SLO configuration and in which the horizontal width of a frontal fundus image on a display unit is set to be large relative to the horizontal width of an OCT image so as to display the frontal fundus image with an angle of view similar to that of a fundus camera. In general, a segment of interest in an OCT image is often the macula and the optic disc of the fundus. The shorter the distance from the position in which the optical path length of measurement light and the optical path length of reference light match (hereinafter, a coherence gate position) to an observed segment, the higher the sensitivity of the observed segment shown in a tomography image produced through imaging.
However, as the fundus has a curved shape, bringing the macula and the optic disc close to the coherence gate position could possibly cause a boundary between the posterior vitreous body and the retina to straddle the coherence gate position. In this state, a tomographic image undesirably shows an aliased image together with a real image in the vicinity of the coherence gate position. As a result, a frontal fundus image obtained based on luminance information of the tomographic image in a depth direction also shows an image abnormality in a ring-shaped region corresponding to an aliased portion.